The present application relates to a hydraulic system having a hydraulic supply, a consumer and having a control valve, which is arranged between the hydraulic supply and consumer and is in communication with the consumer by means of a first line and a second line, it being possible for the control valve to be switched into different positions, and the control valve connecting the hydraulic supply to the first line in at least one position.
Various embodiments of hydraulic systems of this type are known. The hydraulic supply used is generally a pump, the delivery side of which can be connected to the consumer by means of a control valve. The control valve may be designed, for example, as a longitudinal or rotary slide valve. In known hydraulic systems, a first line and a second line lead from the control valve to the consumer and back from the consumer to the control valve, respectively. In this arrangement, it is usually provided that alternatively either the first or the second line is connected to the delivery side of the hydraulic supply, and that the line which is not used as a delivery line serves as a return line.
Irrespective of their particular design, known hydraulic systems are afflicted with the drawback that considerable pressure losses occur in the hydraulic medium as it flows through the control valve, resulting in corresponding losses of power.
Therefore, one object of the present application is to develop a hydraulic system of the type described in the introduction in such a way that the pressure losses in the hydraulic medium flowing through the hydraulic system are reduced.
This object is achieved by a hydraulic system having a first valve, which is in communication with the first line and the second line. Furthermore, a third line, which serves as a further return, is in communication with the first valve and does not lead to, or open out in, the control valve, is provided, the first valve being connected in such a manner that when pressure is applied to the first line it opens up a connection between second line and third line. The result of this arrangement is that not all of the return is routed via the control valve, with the associated pressure losses. The opening-up of the connection between the second line, which in this case serves as a return, and the third line, which likewise serves as a return and is not routed via the control valve, but rather preferably passes the hydraulic medium directly into the tank, results in some of the hydraulic medium experiencing only slight pressure losses. The additional reserves of power obtained as a result are available to the consumer and can be used, for example, for operation of the tool of an excavator.
The valve arrangement according to one embodiment may be single-acting. However, a double-acting design can be particularly advantageous and may be provided in a situation in which, depending on the position of the control valve, either the first line or the second line is connected to the delivery side of the hydraulic supply, and in each case the other line serves as a return line. Accordingly, in a further configuration it is provided that, furthermore, a second valve, which is likewise in communication with the third line, and is also in communication with the first line and the second line and is connected in such a manner that when pressure is applied to the second line the second valve opens up a connection between first line and third line, is also provided. In this case, the second line serves as a feed line and the first and third lines serve as return lines.
A particularly compact arrangement results if the first valve and the second valve are arranged in a common valve block.
The first valve and/or the second valve are advantageously designed as spring-loaded seat valves or as slide valves, which are preferably likewise spring-loaded. Other variants are also conceivable. The control valve is preferably a slide valve. In principle, any desired variants of the control valve are also conceivable.
It is particularly advantageous if the first valve and/or the second valve is designed with additional features as discussed herein.
The consumer of the hydraulic system may, for example, be a piston-cylinder unit which is in communication with the tool of a working machine, for example an excavator, or any other desired drive unit. Examples of suitable tools include a shears mechanism or a hammer, or an arm with scoop cylinder, an arm with double tongs and the like.
The present application may also relate to a valve having a first port, second port and having a third port, and having a first valve body, which can be moved into different positions and in a closed position blocks off a connection between the second port and third port and in an open position opens up a connection between the second port and third port, the valve body being in communication with the first port and being arranged in such a manner that the valve body is moved into the open position when pressure is applied to the first port. The third port can be used for additional discharging of the hydraulic medium, for example into a tank, without the hydraulic medium which is returned in this way passing through the control valve of a hydraulic circuit. It is in this way possible to actively reduce pressure losses in the return.
The valve may also be designed as a double-acting valve. Accordingly, it is possible to provide for there to be a second valve body, which can be moved into different positions and in a closed position blocks off a connection between the first port and the third port and in an open position opens up a connection between the first port and third port, the valve body being in communication with the second port and being arranged in such a manner that the valve body is moved into the open position when pressure is applied to the second port. The valve according to this embodiment connects the return to the third port and therefore to a line which is not routed via the control valve.
As has been stated above, the valve is preferably designed as a seat valve or slide valve. In this context, it is possible to provide for the first valve body and/or the second valve body to be a spring-loaded lifter or slide which is accommodated longitudinally displaceably in a valve block of the valve. The first valve and second valve can be realized by a common slide. In one end region, the lifter may have a conically narrowing valve disk, which in the closed position bears against a valve seat of the valve block. Furthermore, it is possible to provide for the lifter to have a disk in an end region and for a compression spring, which is supported between the disk and the valve block, to be provided. The spring is designed in such a manner that the valve body is moved into its closed position when no pressure is present.
The ports of the valve may be designed as bores in the valve block, the longitudinal axes of which bores run parallel to one another.
Furthermore, it is possible to provide for the lifters to be movable in directions running parallel to one another.
Finally, one embodiment relates to a working appliance, in particular an excavator, having the hydraulic system as described herein, and/or having the valve as described herein. The consumer of the hydraulic system may be a piston-cylinder unit or other drive unit of a shears mechanism, a hammer, a scoop, tongs or double tongs and the like. However, the possible applications for the hydraulic system and valve according to the invention are not restricted to these examples. By way of example, a rotary drive is another possible drive unit.
It is particularly advantageous if the valve is arranged on the consumer or on the tool of an excavator or in the immediate vicinity thereof. In a preferred configuration, the hydraulic medium which is returned via the third line does not have to flow around or through any obstacles or further valves, but rather can be discharged directly, resulting in minimal pressure losses in the return.